Thermal plotting apparatus is known in which heat is selectively applied to a thermally reactive sheet to cause a visible image to appear on the sheet. A heated stylus is arranged for movement on a thermally responsive sheet in response to an applied signal to provide a corresponding trace on the plotting sheet. Alternatively, a stylus array confronts the sheet, and the styli are selectively energized to cause formation of a visible image on the sheet. Such plotters of known construction can be relatively complex and expensive, especially if high resolutions are to be achieved.